Method of making phonograph record stampers



June 27, 1944. B. A. PROCTOR METHOD OF MAKING PHONOGRAPH RECORD STAMPERFiled Sept. 19. 1936 2 Sheets-Sheet l Fig.2

\\ I xm ATTORNEY .5

June 27, 1944. PRQCTQR 2,352,285

METHOD OF MAKING PHONOGRAPH RECORD STAMPER Filed Sept. 19, 1936 2Sheets-Sheet 2 Fig. 19 5 INVENTOR. Barron AProcfor ATTORNEYS PatentedJune 27, 1944 METHOD OF MAKING PHONOGRAPH RECORD STAMPERS Barton A.Proctor, Larchmont, N. Y., assignor to B. A. Proctor Company, Inc., NewYork, N. Y., a corporation of New York Application September 19, 1936,Serial No. 101,677

4 Claims.

This invention relates to the production of sound records and has forits general object to expedite the fabrication of phonograph records andto economize in their manufacture, especially by reduction in the timerequired for such fabrication and in the cost of equipment.

More particularly, the novel process herein disclosed effects a notablereduction in the time of manufacture, which has been out to twentyminutes, as compared with the inordinate time of from twenty-four tothirty-six hours required to complete records when made by theconventional method, involving several steps which have been eliminatedby the method of the present invention.

The well-known conventional method comprises the step of recording thesound track upon a wax blank, thus forming the original master, uponwhich is electro-deposited a shell of metal which then becomes themaster, as the stylusproduced original wax master is destroyed duringthe stripping from the electro-deposited sheet, and the wax originalthus lends itself only to the formation of one metal reproduction.

As this metal master, which is called a Stamper, can only be used in onepress at a time, it is necessary to use it as an original master formaking other Stampers, according to the number of presses to be used inmass production of the final playing records, the latter being pressedout of thermo-setting plastic material for sale as the final playingrecords- Each metal stamper is therefore a reproduction of areproduction, and there is a loss of quality due to the severalreplating steps in this conventional process, which need not be furtherelaborated, as its disadvantages are generally recognized.

Under such conditions, particular objects of the present invention are:

To provide an original master record of sturdy structure which goesdirectly from the recording 1 machine to the hydraulic press, in whichsame press any desired number of finished master records (stampers) canbe made therefrom directly, without loss of character such as is causedby the electro-plating steps briefly mentioned already; also to providea sturdy original master record which can be kept indefinitely and maybe used to fabricate other fresh stampers after the earlier stampersbecome worn by excessive use.

A cognate object of the invention is to provide a method of producingthe original sturdy master record in metal, so that it is possible toeliminate over fifty per cent of the manufacturing equipment heretoforefound indispensable in the production of records by the above describedconventional method, including wax temperaturecontrol apparatus, ashaving machine; electroplating equipment; and cleansing, marking andfinishing apparatus.

The present invention avoids the above disadvantages and accomplishesthe above desirable improvements, and others which will be made toappear in the course of the following disclosure, by providing a novelmethod according to which in the first place, a cutter of thecrystal-operated type is employed, having sufficient power to deform asound track of adequate depth and sidewall characteristics in a metallicblank which is of sufiicient hardness to withstand hydraulic pressure ofapproximately 2000 lbs. per sq. inch without essential damage to thesound-groove structure, the latter being characterized by a completeaudio frequency range.

The recorder thus provided makes it possible to utilize for the materialof the blank, in which the sound track is recorded, either a solidmetal, such as aluminum, or a duplex metal blank, pref erably comprisinga layer of metal,v such as tin, in which the sound track is recorded,and a body plate of thin sheet steel.

The layer of tin, or other like suitable metal, may-be electrically, ordeposited by any suitable method, and will be of suitable depth to takethe sound groove. Such a layer has the advantage, over 2. rolledintegral plate, of being absolutely grainless, and characterized byhomogeneous molecular distribution of the metal. In other words, the tinlayer is free from cracks and from stresses due to rolling, and fromother disturbances of the molecular arrangement and other imperfectionswhich are caused by the rolling process.

The steel backing of this novel record blank provides additionaladvantages, in that it prevents creeping or flow of the metal underhydraulic pressure, and the tin facing has a desirable chemical reactionwith the plastic, as compared with the aluminum.

Owing to the greater hardness of the material used, as compared with thesofter metal ones produced by the electro-depositing process, thematrices made of steel-tin duplex structure wear better than thematrices'made conventionally heretofore. The expansion factor andcontraction factor, under the heating and chilling operations incidentalto pressing records, are considerably less than those of the oldelectro-shells.

Inasmuch as the matrix produced by the novel method of thepresent-invention can be of the same thickness (say .004 of an inch) asthose of electro-plates, the new matrices can be trimmed at theircenters and peripheries as easily as any of the older matrices, so thatthey may be handled by'any plant equipped for that purpose. Because oftheir flexibility, they can be used in crowned dies to accommodatethemselves to the shape of the dies, from which they take a slightlyarcuate shape.

In making a stamper from the original matrix, solid metal or composite,several layers (say ten) of a sheet material such asBakelite-impregnated paper coated on its upper side with Bakeliteimpregnating-varnish are placed in a press under heat and pressure forapproximately fifteen minutes, to be cured, including the requisitechilling, and the assembly is then removed for trimming at its edge. Thecenter hole is moulded, and the stamper thus completed can be duplicatedby the similar production from the original matrix of as many stampersas are required for use in the presses being run.

The invention provides for mixing with the impregnated Bakelite ametallic powder such as aluminum or bronze in order to increase thethermal conductivity of the mass both in the heating and cooling steps,and thereby to reduce cost of manufacture still further, the metalparticles also serving to reinforce the mass and add to its stability.The metallic powder also serves to aid in preventing distortion of thefinished stamper when subsequently used in stamping the final records.

An important factor in such prevention of distortion of the stamperresides in its laminated structure, which retards the freedom of flow ofthe (Bakelite) thermosetting material, which might otherwise result indistortion of the finished stamper, as will be readily understood whenit is realized that the shrinkage is of a very high order.

Here also the factor of expansion and contraction respectively under theheating and chilling during the operation of pressing records isconsiderably less than in the case of the old metal stamper produced byelectrodeposition. The laminated structure also permits a flat stamperto flex to the shape of a crowned die without any such cracking asfrequently accompanied attempts to flex stampers of the conventionaltype.

The last operation in the fabrication of playing records for the marketconsists in pressing thermoplastic material of any suitable character,such as cellulose acetate, with the stamper, in the same die as that inwhich the stamper has been produced by pressure of the metal masteragainst the blank for the stamper, it being understood, however, thatbecause the playing records are of slightly smaller diameter, aconfining ring is used between the upper and lower stampers which areemployed in impressing records upon the obverse and reverse sides of thefinal record blank material.

In the accompanying drawings:

Fig. l is a fragmentary, detail view in front elevation of a recordingmechanism adapted to be used in carrying into effect the method of thepresent invention.

Fig. 2 is an elevational view partly in section, of a press used in thefabrication of stampers and records according to the novel method of thepresent invention, the press being illustrated in open position with thedie elements, master, and stamper components assembled in position forthe operation of producing a stamper;

Fig. 3 is a fragmentary view in elevation, partly in section, showingthe dies closed upon a stamper matrix formed by pressure of thecomponents as illustrated in Fig. 2;

Fig. 4 illustrates in fragmentary, detail form, the ends of an assemblyof components for a stamper, broken away to show the typical laminatedstructure of the stamper in course of formation;

Fig. 5 is a view similar to Fig. 4, illustrating the compressedcomponents of Fig. 4;

Fig. 6 is a view similar to Fig. 3, but showing two stampers, associatedwith a pair of die members, and closed upon a blank of thermo-settingmaterial, such as cellulose acetate, in the course of making a two facedrecord;

Fig. 7 is a detail view in vertical section taken across the diameter ofan assembly including a blank of thermo-setting material ready to bepressed between two stampers associated with crowned dies in theproduction of a two-faced record;

Fig. 8 is a fragmentary, detail view in greatly enlarged verticalsection of one end of a metal record, with part of a sound trackrecorded therein;

Fig. 9 is a similar view of the same, but showing also the stamper blankwhich has been pressed thereinto;

Fig. 10 is a similar view showing in detail the left-hand end of thesame disposition of stampers on each side of a blank, as shown in Fig.6; and

Fig. 11 is a fragmentary detail view of a portion of a duplex metalrecord blank having a body of sheet steel and a face layer of tin inwhich a sound track has been recorded.

In a now-preferred embodiment of the invention illustrated in thedrawings, the parts designated by the reference characters I, 2, 3, 4and 5, respectively, are the base, plunger, plate, side pillars and headof a press in which the dies 6 and 1 are ready for use in pressing astack of paper stamper-component laminae 8 together with Bakeliteimpregnant for the purpose of forming a master or stamper from the metalrecord R in which the sound track has been recorded.

Each of the dies 6 and 1 is cut away near its margin to form a groove,as 9, I0, of annular form, and each of the grooves has seated therein asuitable shear member II, I 2 respectively, the shear l2 taking the formof a ring with an inwardly disposed cutting edge as l3, and the ring IIin die 1 serves as an abutment shear against the upper face of which thecutting edge I 3 forces and pinches the material. The dowel l4, set atIS in the material 20 of the central hole of the stampers and of therecords.

When the plunger 2 rises and forces the die I, heated suitably, as bypipes 2|, against the die 6, and compresses the stack 8 of laminaetherebetween, the master stamper assumes the form shown in Fig. 3, andthe record 28 now contains a replica in complete reverse detail of thesound track which had already been formed in the metal blank R by asuitable recording operation, such as that indicated schematically inFig. 1, where C is a recorder head of the crystal-recording type, R isthe master record blank having a body 38 of sheet steel with a facelayer 39 of tin (see-Fig. 11), in which the sound track is beingmade,and T is a rotatable table of conventional form.

Reference may be had to my co-pending application Serial No. 38,032 fora more detailed dis closure of a preferred type of crystal-recordingmechanism in which the master record may be made.

With respect to the structure and fabrication of the stampers, the stepsincluded in the preferred method for their fabrication as indicated inFigs. 2, 4 and 5 may be summarized as follows:

Several layers of Bakelite impregnated paper, I8 (see Figs. 4 and 5),each of which is coated on one side, as at I9, with Bakelite varnish,are

die, acts to mold the assembled. as shown in Fig. 2 at 8 upon the recordR. which has been produced as indicated in Fig. 1. The face of thismaster which contains the sound track is presented upwardly. as in Fig.8, and preferably the record R is either of solid metal, such asaluminum. or of duplex metal constituted by a sheet steel base and a tinfacing in which the sound track has been recorded.

In Figs. 4 and 5. the stippling observable throughout the layers I8 andI9 indicates the presence therein of finely divided metallic powder,such as aluminum or bronze powder.

This. as already pointed out briefly, serves to increase theconductivity and to cut down the time occupied in heating or chilling,so that the cost of manufacture is thus reduced. It also adds to thestability of the mass due to the reinforcement thereof afforded by themetal particles. The presence of the metal particles, furthermore,checks the freedom of flow of the thermo-setting material and soavoidsdistortion. It does not, however, interfere with suitable flexing of thestamper when associated with a crowned die as illustrated in Fig. '7.

When the composite blank 8. composed of layers |8 and I9, has beencompressed, as shown in Fig. 5. the stamper structure thus produced isnotably stronger than an electrolytically produced shell, andaccordingly more, and better, playing, or final, records can befabricated with the use of such a stamper in the dies.

In Fig. 6, two such stampers are shown, as at 2| and 22 respectively,above and below a blank A of cellulose acetate, which is being pressedtherebetween to form a double faced record. The

blank A is of somewhat smaller diameter than the masters 2| and 22, and.accordingly, each die 23, 24 is formed with a peripheral flange 25 whichis of annular form, suitable to constitute an abutment, and thus toconfine the plastic material, and each of the duplex ring componentsserves also as a retaining ring for the master which it surrounds, theflanges 25 extending inwardly over the rims of the masters, as shownclearly in Fig. 6.

There is substantially no Waste of material in the fabrication of thefinal product. and its advantages in point of economy are of anoutstanding character.

As already indicated, the process and the in- F strumentalitiesutilized, lend themselves to the correct fiexure of the initially flatstampers into convexly arcuate form by association with crowned dies inthe production of concavely arcuate records, impressed for playing, andan example of such use is illustrated in Fig. 7, in which the masters 3|and 32 are used in a press like that shown in Fig. 6, except thatcrowned dies are being used, the flexibility of the master componentsmaking such conformation ,to the crowned dies possible.

Similarly, the blank 33 of Fig. 7, composed of cellulose acetatematerial, takes readily the impress of the masters 3| and 32 thus flexedto arcuate form, and possesses all of the desirable features to bepredicated of a concavely arcuate record.

The Fig. 6 assembly of masters 2| and 22 is shown in detail on a largerscale in vertical section in Fig. 10 where the clearly impressed soundrecord pressed in the two faces of the blank A by the superimposedmasters is well illustrated.

Fig. 8 shows, in similarly enlarged detail a master original record R.comprising a body 34 of solid metal, in which the sound track 35 hasbeen deformed by operation of a crystal recorder head or mechanism asshown in Fig. 1: and Fig. 9 shows said master in course of use to form anegative stamper record 8 which has been made by pressing together alaminated assembly of the components shown in Figs. 2-5. and describedabove. with the aforesaid original master R.

Each stamper 8 so produced may be used in the manner shown at 2| and 22or 3| and 32, in forming an indefinite number of the cellulose acetate,or like records as shown at A in Fig. 6, or as shown in Fig. 10. whethersingle-faced or doublefaced. and the records so produced. both stampernegatives and final playing records. preserve with remarkable fidelity.in their sound tracks, the fine qualities of the originals of which theyare replicas. being greatly superior to the equivalent replicasfabricated from electrolytically deposited stampers.

I have described what I believe to be the best embodiments of myinvention. I do not wish, however. to be confined to the embodimentsshown, but what I desire to cover by Letters Patent is set forth in theappended claims.

I claim:

1. In the fabrication of sound records, the method of forming alaminated stamper which comprises the steps of dispersing a finelydivided metallic powder in a thermosetting plastic material, applyingthe plastic material containing the metallic powder to the surface of asheet of soft, fibrous material to form a coating. and heating thetreated sheet material to condition it to receive the impression of asound track in the coated surface thereof.

2. In the fabrication of sound records. the method of making a stamperwhich comprises the steps of mixing a finely divided metallic power in athermo-sett ng plastic material in proportions to obstruct the flow ofplastic and to promote equable heat transfer during curing, impregnatinga disc of soft fibrous material with the resulting plastic mixture andheating and simultaneously compressing the impregnated disc to conditionits surface to receive the impression of a sound track therein.

3. In the fabrication of sound records, the method of making a lstamperwhich comprises the steps of mixing a finely divided metallic powder ina thermo-setting plastic material in proportions to obstruct the fiow ofplastic and to promote equable heat transfer during curing, impregnatinga plurality of separate fibrous laminae with the resulting plasticmixture and heating and simultaneously compressing the laminae togetherto form a stamper and condition the outer face thereof to receive theimpression of a sound track therein.

4. In the fabrication of sound records, the method of making a stamperwhich comprises the steps of mixing a finely divided metallic powder ina thermo-setting plastic material in proportions to obstruct the flow ofplastic and to promote equable heat transfer during curing. impregnatinga plurality of paper discs with the resulting plastic mixture, arrangingthe impregnated discs to form a stack, coating the surface of the outerdisc with a thermo-setting varnish mixed with finely divided metallicpowder. and heating and simultaneously compressing the discs together toform a stamper and condition the coated surface of the outer disc toreceive the impression of a sound track therein.

BARTON A. PROCTOR.

